This is considerably more complicated than installing a kitchen sink or basin faucet. You'll need an Allen wrench, a multi-head screwdriver, an adjustable wrench, copper cutters, a torch, fire-resistant shielding, and perhaps PEX cutters and crimpers to complete this project.
To replace the shower faucet, you'll need to get to the shower's backside. If you're going to tile the front, you may reach it from the front and finish the work that way. Because most showers lack shut-off valves, you'll have to turn off your home's main water supply and empty your pipes.
The handle and faceplate of the faucet should be removed at this time.
After that, make a cut into the wall from either the front or the rear of the shower enclosure.
In order to cut out the old valve and get a torch in there to solder the new faucet into place, you'll need a hole that's big enough. Depending on how old the home is, you may have PEX water lines.
However, you should still have a copper riser from the water line to the showerhead. Unless you purchase a valve that requires you to solder the copper tube directly to the faucet, you will need to solder the copper tubing to the fitting that will be threaded onto the faucet before continuing. If this is the case, be careful to remove the stem to avoid any issues later on as a result of the internal components melting.
After you've removed the old shower valve, you'll need to take measurements to ensure that the new faucet will fit properly in its place.
If this is the case, you will need to trim the front of the shower to ensure that it is correctly installed. Before threading the brass by copper or brass by PEX fittings onto the faucet, spray Teflon on the threads to prevent corrosion. There are certain instances when a single shower valve may be used for both a shower and a tub/shower system. If this is the case, a brass plug should be provided that may be threaded into the bottom of the valve.
Fix the faucet firmly to a piece of wood or a 2x4 with screws.
The faucet should be placed in the same position as the previous faucet once you have finished installing the new fittings. Connect the water lines to the new unit by soldering or crimping them together. Remove the old showerhead and insert a nipple and cap into the female joint to complete the installation. Now close any doors or windows that were opened to drain the home and re-connect the water supply to the residence.
Check for any leaks that may have occurred. If everything seems to be in working order, you may turn off the water and empty the home. Then remove the nipple and cap and insert the shower arm and head into the female thread of the showerhead. After you've finished installing the faceplate and handle, turn the water back on. Check to verify that the handle is in the correct position. If this is the case, remove the handle and rotate it.
Leaks should be repaired immediately once they are discovered; the handle and faceplate should not be installed until they have been thoroughly tested.
If your previous shower had a two-handle design and you are replacing it with a single lever design, you will need to install a plate that will cover the holes in the old faucet before you can proceed. Delta sells this product, which can be found at most hardware shops.